Your Brain on bin Laden: Why Vengeance Is So Sweet

Schadenfreude — joy in another’s suffering or death — is a vicious pleasure. But it’s far less guilt-inducing when the victim is an enemy like Osama bin Laden, who has gotten his just deserts. Does that make it all right?

As I’ve noted here earlier, there are good evolutionary reasons for the human taste for vengeance: oddly enough, our best qualities, such as altruism and cooperation, probably could not have survived in nature without the existence of revenge — a way to detect and punish the members of the group who either don’t pitch in or actively cause harm.

The act of penalizing rule-violators — anyone from the slow walker on a New York City sidewalk to the leader of the terrorist group behind the 9/11 attacks — has been labeled “altruistic punishment,” by researchers. It’s “altruistic” in that the person doing the punishment takes on the risks of enforcement himself, while the benefits go to society as a whole.

Of course, the Navy Seals who killed bin Laden were acting in service of their country, not as vigilantes. But the very existence of vigilantism speaks to the strong human desire to make the bad guys pay, even at great personal cost. Immediately after 9/11, a not-insignificant number of Americans responded by saying they would happily pay money for the chance to kill bin Laden themselves. And many young men and women joined the armed forces after the 2001 attacks, knowing well that they could wind up sacrificing their lives to protect their country.

Brain-imaging research shows that when engaging in altruistic punishment — for example, paying money to make sure someone who has not been fair to you in a game gets no cash — the pleasure regions of the brain light up.

So why would we be wired to perceive the punishment of rule-violators as rewarding? Researchers have tried to understand the evolution of altruistic punishment in the context of cooperative behavior. A theoretical situation called the “Prisoner’s Dilemma” turns out to shed a lot of light on the problem. In this scenario, two criminals have been arrested. If both refuse to snitch, they will each get only six months in jail because the police won’t have evidence to support a heavy charge. But the first person to rat out his partner in crime for a serious offense goes free while the other guy gets 10 years. If they both confess simultaneously, they’ll each get five years. (The sentence lengths involved in the situation can vary to test different mathematical outcomes, but the overall principle remains the same.)

In one such study, recently conducted at University College London, scientists found that when people witnessed the snitches receiving painful electric shocks — even though the study volunteers weren’t the ones meting out the justice themselves — the pleasure regions of their brains were activated (but only in men).

When considering society on the whole, however, it gets much more interesting when you run this game repeatedly, trying to determine whether self-interest or honor among thieves is a better strategy. As Jonah Lehrer describes it in a recent Wired blog post:

When the game is simulated for thousands of sequential rounds, it turns out that the most effective basic strategy is an approach known as “tit for tat.” The rules of tit for tat are incredibly simple: unless provoked, the prisoners will cooperate (and not confess). However, once they are provoked, they will seek out revenge, Old Testament style. This helps ensure that defection is discouraged, that people know their cheating has consequences. And this is why the brain, at least in young men, takes so much delight in the pain of bad people. An eye for an eye feels great.

What this means, in evolutionary terms, is that cooperative creatures can survive and beat out selfish ones — but only if the cooperative ones have some way of punishing selfishness.

But it turns out that there’s an even more successful strategy than “tit for tat,” known as “generous tit for tat.” The generous version responds to noncooperation with the same — but if the other person starts to cooperate again, so does it. This strategy adheres to the “give the other guy a break” school of thought, by not always punishing defection.

Generous tit for tat may be more relevant to human behavior than the straightforward version — most of our disputes do not descend into Hatfield and McCoy revenge cycles, thankfully.

And as we consider bin Laden’s fate, we should not forget the need to temper our exuberance over justice with feelings of mercy. Bin Laden may not deserve any kindness — but the rest of humanity requires it.